AEF0217 in Participants With Down Syndrome

Inclusion Criteria: * 1\. Male and female. For males: Throughout the trial and until the end of the trial, male participants should refrain from donating sperm and, if sexually active, use double-barrier contraceptive methods (i.e., male condoms and spermicide), or the female partner must use the same highly effective contraceptive methods as female trial participants . For females: Female participants of childbearing potential, defined as having a menstrual cycle that is confirmed prior to enrolment, must use highly effective contraception throughout the trial and until 3 months after the last dose of the trial intervention, be sexually abstinent, or have a vasectomized partner. * 2\. Age ≥16 to ≤32years. * 3\. BMI ≥18.0 and ≤35 kg/m2. * 4\. Clinical diagnosis of Down syndrome (full trisomy 21 or translocations) documented by chromosomal analysis (karyotyping). * 5\. Must be independently mobile and have sufficient vision and hearing to participate in the trial evaluations. * 6\. IQ \>35-70 measured with Leiter-3. Individuals with IQ from \>35 to \<40 must have adequate cognitive and behavioural abilities according to the judgment of the principal investigator. * 7\. VCI of WISC-V language test score \>4, based on mental age (estimated via IQ). * 8.Must be able to understand most of the time and to express if he/she does not understand to the extent that he/she can accept the trial procedures. Must not use other forms of communication, signs, symbol boards, or devices as …